Substituted 2,3,7-triazabicyclo[3.3.0]oct-3-ene-4-carboxylic acid esters react with chlorine and bromine to give the corresponding 4-halo-2,3,7-triazabicyclo[3.3.0]oct-2-ene-4-carboxylates. Heating of the latter to 120 degreesC under reduced pressure leads to elimination of nitrogen molecule and formation of 6-halo-3-azabicyclo[3.1.0]hexane-5-carboxylates.
Substituted 2,3,7-triazabicyclo[3.3.0]oct-3-ene-4-carboxylic acid esters react with chlorine and bromine to give the corresponding 4-halo-2,3,7-triazabicyclo[3.3.0]oct-2-ene-4-carboxylates. Heating of the latter to 120 degreesC under reduced pressure leads to elimination of nitrogen molecule and formation of 6-halo-3-azabicyclo[3.1.0]hexane-5-carboxylates.